1. Field of the Invention
The present disclosure relates to liquid crystal display technology, and more particularly to a LED backlight source and a liquid crystal device (LCD).
2. Discussion of the Related Art
With the technology revolution, backlight technology of LCDs are developed. Typical LCDs adopt cold cathode fluorescent lamps (CCFL) as the backlight. However, as the CCFL backlight is characterized by attributes including low color reduction ability, low lighting efficiency, high discharging voltage, bad discharging characteristics in low temperature, and also, the CCFL needs a long time to achieve a stable gray scale. As such, LED is a new developed backlight technology.
Regarding the LED backlight source, a plurality of LED strings are arranged behind the liquid crystal panel. Each of the LED string includes a plurality of LEDs serially connected. Specific driving circuits are needed to provide driving voltage to the LED strings.
FIG. 1 is a schematic view of a conventional LED backlight source adopted in LCDs. As shown, the LED backlight source includes a backlight driving integrated circuit 110, a boost circuit 120, a plurality of LED strings 130. Each of the LED string 130 includes a plurality of LEDs and a resistor R1.
The boost circuit 120 is for boosting the inputted direct current (DC) voltage to drive the LED strings 130. The backlight driving integrated circuit 110 controls the duty cycle of the driving signals provided to the boost circuit 120 according to the voltage at two ends of the resistor R1 of one of the LED string 130. In this way, the voltage provided from the boost circuit 120 to each of the LED strings 130 is controlled.
In addition, an over-current protection end of the backlight driving integrated circuit 110 connects between the boost circuit 120 and the resistor R2 to provide the over-current protection function. When one of the resistor R1 of the LED strings 130 is short-connected, the current of one of the LED string 130 may be extremely huge such that the output power of the boost circuit 120 may increase dramatically. Under the circumstance, the electrical components within the driving circuit may be burn out and even results in fire. Thus, the output power of the boost circuit 120 has to be reduced when the resistor R1 of the LED string 130 is short-connected so as to enhance the safety and reliability.